Aspergillus fumigatus secretes several glycoprotein enzymes into the growth medium. The oligosaccharide chains of two of the enzymes, an alpha-glucosidase (alpha-gluE) and a Beta-glucosidase, have been characterized and found to be almost identical to mannose and glucosamine chains from a variety of sources. Glycoproteins mannosylated in an in vitro mannosyl transferase reaction were also analyzed and the sugar chains seem to be identical to those of the secreted enzymes. A purified intracellular alpha-glucosidase (alpha-gluI) has the same enzymatic properties as alpha-gluE, but a higher molecular weight and a more unstable conformation. Anti-alpha-gluE serum does not react with alpha-gluI and so the relationship between the two enzymes is not yet certain. Using anti-alpha-gluE coupled with peroxidase as a cytological probe, alpha-gluE has been located only on both sides of the plasma membrane and the outer cell wall, which may be indicative of the site of synthesis of alpha-gluE. Further work will be designed to: (1) determine the intracellular sites(s) of synthesis and glycosylation; (2) determine the relationship between glycosylation and secretion; (3) obtain mutants deficient in secretion or glycosylation.